Answers

The way that i did was when the black rider is looking away from you through a rock behind in the direction that you came from, you want to have a good hiding spot so they dont see you. they go in the direction that you threw the rock ( L2 then O) and stay for about 5- 7 seconds. run until you find a hiding spot and do it all over again. this is the hardest part in the game so dont feel like you should be getting it on your first try. OH AND SAVE EVERY SEVERAL MINUTES OR YOULL BE DOING IT ALL OVER AGAIN>

What i did is that when you stop talking to master Gamgee you go over to the silo and hide behind it when a dark rider comes you can either throw a rock over the house or wait for it to leave then you AND I QUOTE sneak over to the open chicken coop hide behind that then you move to the water sneak forward and then you'll meet Sandyman's mill there will be a dark rider on the other side throw rocks then sneak across the bridge then run to Bywater